Non genuine claim-a to z

Hai,

I am a uk seller selling in on other amazon market places .Recently faced a A to Z guarantee claim stating product not received. But tracking number showing as product delivered on 12/12/2019 and amazon refund the buyer based on A to z claim on 16th. Appealed and amazon granted the claim in favour of customer even the proof is there 02/01/2020.

Customer even agreed the item delivered into his chosen area.

What I can do .I lost £57 in sales and product and shipping.

I don’t know why amazon doing this even proof provided and email conversations proved the same .

Anybody able to help or advice.